Make processingRetryTimeout configurable

[leszko]

It was set to 2 seconds which is too low for Live Video to Video (Realtime Video).

[codecov]

Codecov Report

Attention: Patch coverage is 5.55556% with 17 lines in your changes missing coverage. Please review.

Project coverage is 32.20410%. Comparing base (66ab0f9) to head (ee854cc).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
cmd/livepeer/starter/starter.go	0.00000%	12 Missing ⚠️
server/ai_session.go	0.00000%	3 Missing ⚠️
server/ai_process.go	0.00000%	2 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3387         +/-   ##
===================================================
- Coverage   32.20719%   32.20410%   -0.00309%     
===================================================
  Files            147         147                 
  Lines          40640       40647          +7     
===================================================
+ Hits           13089       13090          +1     
- Misses         26779       26785          +6     
  Partials         772         772                 

Files with missing lines	Coverage Δ
cmd/livepeer/livepeer.go	56.03448% <100.00000%> (+0.19032%)	⬆️
core/livepeernode.go	74.01575% <ø> (ø)
server/ai_process.go	0.59778% <0.00000%> (-0.00102%)	⬇️
server/ai_session.go	2.51799% <0.00000%> (ø)
cmd/livepeer/starter/starter.go	7.43494% <0.00000%> (-0.01848%)	⬇️

... and 2 files with indirect coverage changes

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Files with missing lines	Coverage Δ
cmd/livepeer/livepeer.go	56.03448% <100.00000%> (+0.19032%)	⬆️
core/livepeernode.go	74.01575% <ø> (ø)
server/ai_process.go	0.59778% <0.00000%> (-0.00102%)	⬇️
server/ai_session.go	2.51799% <0.00000%> (ø)
cmd/livepeer/starter/starter.go	7.43494% <0.00000%> (-0.01848%)	⬇️

... and 2 files with indirect coverage changes